Pipe-laying method



April 15, 1958 J. L.. McELvANY PIPE-LAYING METHOD 2 Sheets-Sheet l Filed March 8, 1954 1477' GEA/Ey JNVENTOR. J2/wes L. MC/LV/Wy,

J. L. MCELVANY PIPE-LAYING METHOD April 15, 1958 2 Sheets-Sheet 2 Filed March 8, 1954 IMS L. Mcmmny,

INVENTOR.

rraQ/vey BY TQ St..l tes Patentrhice PlPlE-LAYING METll-ID .lames lLeon McElvany, El Centro, Calif. Application March S, 1954, Serial No. 414,758 6 @Claims (Cl. lll-) This invention relates to a means and method for laying drainage pipe underground and is directed particularly to the problem of laying drainage pipe in watersoaked soil.

The invention has special utility for meeting a drainage problem such as exists, for example, in the Imperial Valley in southern California. This region, which is largely below sea level, has in recent geological time been a part of the gulf of lower California a-nd a table of salt water lies close to the surface of the ground in many parts of the region. It has been found that land which would otherwise be nearly useless can be reclaimed for agriculture by laying drainage pipe to draw off the water to some lower area. When such drainage pipe is installed it is possible to remove excessive salt from the soil by repeated irrigation. Alfalfa is one of the valuable crops that can be grown, the climate permitting several crops of alfalfa to be harvested throughout the year. Since alfalta roots penetrate deeply into the soil and since salt water is fatal to alfalfa, it is especially important in preparing soil for alfalfa to place the drainage pipe a substantial distance under the surface of the soil.

It has been found that good results may be obtained by a drainage system composed of pipe made in short sections of some ceramic or cement mixture. Such pipe sections are commonly called tiles In a tile drainage system the tiles interlock end to end with unsealed joints to permit the ingress of water and are imbedded in a bed of gravel to permit free drainage of water from the adjacent soil. A tile system of this character is especially desirable in comparison with open drainage ditches because the drainage pipe does not interfere with cultivation and also because no maintenance is required to keep the drainage system in good condition.

In relatively dry soil it is a simple matter to dig a trench, pour a thin layer of gravel into the bottom of r the ditch, lay the pipe setcions end to end on top of the gravel, add more gravel to surround the pipeline, and then refill the remaining depth of the trench with soil. PPhe difficulty, however, is that the soil in this region is wet all the time and the trench must be dug in wet mud. To make the problem even more dicult, in many instances the trench extends through a regio-n of quicksand.

Heretofore the problem of laying a drainage line under these conditions has been approached by using a poweractuated trench digger of the wheel type with a narrow housing trailing immediately ybehind the trench digger.

The housing which is of a width to completely lill the trench is open along the bottom and has vertical side walls that extend above ground level. A shallow layer of gravel is deposited in lthe bottom of the trench at the front end of the moving housing and a workman standing inside the housing lays the successive tiles or pipe sections by hand on the gravel. At the trailing end of the moving housing more gravel is added to a level above the laid pipe sections thus completely imbedding the pipe in a bed of gravel. The trench is then filled in behind the moving housing, usually by means of a bulldozer.

This prior method has certain disadvantages which are apparent in even moderately damp soil and which make the method impractical and inoperative in excessively wet soil and quicksand. The difficulty is that the pipe sections do not remain in the correct positions in which they are placed by the workman inside the housing. Even when each of the sections appears to remain in its proper place it will be found that the pipe sections actually move out of place to develop serious gaps. Gravel and earth fall into the gaps to block up the interior of the pipe and thus make the whole system inoperative.

The present invention is based on the discovery that defective positioning of the laid pipe arises from two different causes. One cause is that mud surges upward through the open bottom of the traveling housing into the space on each side of each newly laid pipe section between the pipe section and the adjacent side wall of the moving housing. The intruding mud has an adhesive effect between each side of the pipe section and the adjacent housing side wall, which adhesive effect tends to cause the pipe section to be dragged along with the housing. In this manner a correctly positioned pipe section will s ift longitudinally to develop a serious gap between two successive pipe sections in the laid pipe.

The other cause for defects in the drainage line is upheaval force at the bottom of the trench against the underside' of the through excessively wet soil or quicksand. The more tin-id the soil the greater the freedom for the hydrostatic pressure of the column of mudon each side of the housing to be transmitted to the mud immediately under the open housing at the bottom of the trench. This upward hydrostatic thrust or upheaval force at the bottom of the trench tends to throw each successively laid pipe section upward and commonly results in such upward tipping of a laid pipe section as to `create a fatal gap in the pipeline.y Unfortunately the upheaval action can occur after the pipe section is covered with gravel prior to the introduction of soil to completely lill the trench.

The general object of the invention is to provide a method and an apparatus to meet the problem of installing a tile drainage line in wet soil with special reference -to these two causes for separation and mis-alignment'of the pipe sections. This broad object is accomplished in major part by continuously applying force to the successively laid pipe sections in such manner as t0 keep the installed pipe under continuous longitudinal compression until the installed pipe is weighed down by the final step of ling the trench. In the preferred practice of the invention, the broad object is further promoted by employing `a moving housing that has a bottom wall arrangement effective to prevent the operation of upheaval forces. ln this regard a feature of the invention is the concept of providing a moving gravel-packing zone for the deposition of gravel under and around the pipe as fast as the bottom of the trench is exposed by the traveling lbott-om wall of the housing. When gravel is deposited in the trench under the successively iaid pipe sections -as fast as the bottom of the trench is exposed by movement of the bottom wall of the housing, the gravel acts as a spacing means between the bottom of the trench and the underside of the successively laid pipe sections and is effective to transmit upheaval forces to the underside -of the newly laid pipe. The newly laid pipe withstands upheaval force of any magnitude that may be encountered because the pipe sections being mechanically interlocked are effectively immobilized by the longitudinal compression of `the pipeline. Thus the uninterrupted application of longitudinal force against the progressively Patented Apr. l5, 1958 pipe that occurs When the trench cuts 'C' lengthened pipeline precludes any possibility of undesirable gaps occurring between the laid pipe sections.

A special 'object of the invention is to provide means for applying longitudinal force to the successively added pipe sections in such manner that the periods of force application to the successive pipe sections overlap and to do so in such manner as to provide room for continually adding new pipe sections to the longitudinally stressed pipeline. This special object is accomplished by using a combination of a first force-applying means that engages the `front end of each newly added pipe section and a second force-applying means that grips the newly added pipe sections from their opposite sides. The initial longitudinal force on each successive pipe section is applied at the forward end of the pipe section by the rst force-applying means and subsequently the second force-applying means grips the same pipe section from its opposite sides. For a brief period of time each pipe section is engaged by both the first and second force-applying means and then the first force-applying means is shifted forward to permit the introduction of a new pipe section against which the first force-applying means can be moved.

A still further object of the invention is to provide an eiiicient centralized master control for the two forceapplying means. In the preferred practice of the invention the two force-applying means take the form of pneumatic rams and the master control governs the valves of the pneumatic rams for the desired cycle of operation by the rams against the successively added pipe sections.

The above and other objects and advantages of the invention will be apparent in the following detailed `description of the presently preferred practice of the invention taken with the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative:

Fig. 1 is a diagrammatical view of the presently preferred embodiment of the apparatus of the invention in the process of laying a drainage line of pipe;

Figs. 2, 3 and 4 are diagrams illustrating different stages in the cycle of operation of the two force-actuating means for maintaining the pipeline under longitudinal compression during the laying operation;

Fig. 5 is a fragmentary transverse section taken as indicated by the line 5-5 of Fig. 1 and the angular line 5-5 of Fig. 6;

Fig. 6 is a plan view of a yoke that carries clamp means to grip the successive pipe sections from opposite sides, the yoke being viewed as along the line 6 6 of Fig. 5;

Fig. 7 is a perspective view of `one of the two clamp means;

Fig. 8 is a perspective view of a pusher plate and an associated central ram for applying pressure against the end of a pipe section;

Fig. 9 is a diagrammatical view of the centralized control or master control system for the force-applying components of the apparatus; and

Fig. 10 is a face view of the master cam disc in Fig. 9.

Fig. l shows a line of pipe, generally designated by numeral 20, comprising a `series of pipe sections P laid end to end in a bed of gravel 21 buried in soil a substantial distance below the ground level 22. The individual pipe sections P a-re made of a cement mixture and are adapted for interlocking engagement with each other. As best shown in Fig. 6, each pipe section has an inner cir cumferential ange 23 at one end and an outer circumferential flange 24 at the other end. The two circumferential end anges 23 and 24 are bevelled and engage each 4other in the established pipeline as shown.

The preferred embodiment of the apparatus shown in Fig. l for practicing the new process comprises mechanism and structure carried by a narrow vertical housing, generally designated H, that is connected in tandem to a conventional ditch digger D. The ditch digger D, which may be of the wheel type, digs a trench having a bottom surface 28 and two side surfaces 29, the trench being relatively narrow. The housing H is dragged slidingly along the trench by the ditch digger with a bottom wall 30 of the housing resting on the bottom surface 28 of the trench and with two vertical side walls 31 of the housing positioned close to the two side surfaces 29 of the trench.

The housing H is of a height to extend a substantial distance above the ground level 22, as shown, and has a forward wall 32 to conform to the contour of the ditch digger. The housing also has a rear wall 33 which terminates at the gravel bed 21 and extends upward above the ground level 22. Spaced forward from the rear wall 33 is a relatively short vertical partition 34. The partition 34 is apertured to clear the pipeline 20 and the aperture is preferably provided with a flap or curtain 3S which tends to close the aperture and thereby, in effect, makes the aperture conform to drainage'pipe of different diameters. Thisy vertical partition 34 with its curtain 35 cooperates with the rear wall 33 of the housing to form what may be termed a gravel-packing compartment 36. Gravel is continuously supplied to this compartment by a gravel duct 40 that extends downward from an upper gravel hopper 41. The lower end of the gravel duct 40 is preferably slightly higher than the lower end of the rear wall 33 so that sufficient gravel will be *fed to the gravel compartment to iill the compartment to the level dened by the lower edge of the rear wall.

it is contemplated that the hopper 41 will be kept supplied with gravel as the housing H moves along behind the ditch digger D and that successive pipe sections P will be delivered to the interior of the housing as required to extend the drainage pipeline 2) at the rate of forward movement of the housing. For this latter purpose a suitable chute 42 of V-shaped cross sectional configuration may be mounted in the interior of the housing H, the chute 42 being inclined at a suiiicient angle to cause successive pipe sections P to slide downward thereon by gravity to come to rest against an end stop 43. A workman on the ground beside the trench delivers successive pipe sections P to the upper end of the chute 42 and an operator who carries out the new pipelaying method rides inside the housing H and adds the successive pipe sections to the pipeline.

The successive pipe sections P are taken lfrom the chute 42 by the operator inside the Ahousing H and are deposited on a V-shaped longitudinal pipe guide 4d having longitudinally spaced supports 45 (Fig. 8). The successive pipe sections P are moved rearward on the pipe guide 44 into engagement with the pipeline 2i) in accord with the rate of forward progress of the housing H. The pipe guide 44 is spaced above the level of the bottom wall 30 of the housing to hold the successive pipe sections thereon in longitudinal alignment with the pipeline 20. As each successive pipe section P in contact with the forward end of the pipeline moves rearward from the end of the pipe guide, each pipe section is temporarily supported at its front end by the pipe guide and is supported at its rear end by interlocking engagement with the pipeline. Each new pipe section P is held securely in interlocking engagement with the pipeline by virtue of rearward force applied to the pipe section by the two force-applying means.

One of the two force-applying means comprises a forward central ram, generally designated 49, which includes a horizontal air cylinder mounted on a forward bracket 5l. A suitable piston (not shown) inside the air cylinder 56 is connected to a rearwardly extending piston rod 52 which carries at its rear end a suitable pusher plate 53 (Fig. 8) for contact with the ends of the succesive pipe sections P. The pusher plate 53 may be slidingly supported by the V-shaped pipe guide 4d, the lower edge of the pusher plate being `cut to conform to the configuration of the pipe guide as shown.

As indicated in Fig. 9 the opposite ends of the air cylinder Stlare connected bytwo` air lines 54 with a suitable. three-way valve 55. The three-way valve S5 has the usual relief or discharge port (not shown) and is connected by a supply line 56 with a suitable source of compressed air (not shown). ln a well known manner the three-way valve 55 has a longitudinally movable operating member 57 which has one limit position for driving the ram piston in one direction, an intermediate neutral position and an alternate limit position for driving the `ram piston in the yother direction.

The second of the two force-applying means for acting on the successive pipe sections P may comprise a pair of side rams, generally `designated by numeral 60, positioned on each side of the pipe guide 44. Each of the side rams 6i) includes an air cylinder 61 that has the usual piston (not shown) from which a piston rod 63 extends rearward to a mobile yoke, generally designated by numeral 64.

As indicated in Fig. 9 the two air cylinders 61 may be controlled by a three-way valve 65 that has the usual relief or discharge port (not shown) and is connected by a supply pipe 66 with a suitable source of compressed air (not shown). An air line 67 from one end of the threeway valve 65 is connected by branch air lines eti with one end of each of the two air cylinders o1 and an air line 69 from the other end of the three-way valve is connected by two branch air lines lll with the other ends of the two air cylinders 61. The three-way valve 65 has a longitudinally movable operating member 7i which has one limit position for moving the pistons in the air cylinders in one direction, an intermediate neutral position and an alternate limit position for moving the two pistons in the opposite direction.

The yoke iSd-.is adapted to be reciprocated longitudinally of the housing H by thetwo piston rods 63 and carries a pair of clamp means, each generally designated by numeral 7d, that are adapted to grip the successive pipe sections `13 from the opposite sides of the pipe sections in a releasable manner. The yoke 54, which in this instance is of welded steel plate construction, comprises an arched transverse frame member .76 and two legs '77. The two legs 7'7 extend downward from the opposite ends of the frame member 76 and are formed with lower llanges 7d. The two pistons ofare connected directly to the two legs 77, respectively.

The yoke 64 may be supported by suitable guide means and for this purpose is preferably provided with a suspension bracket 79 on each'side to movably support the yoke from a pair of side rails di? mounted on the two vertical side walls 31 of the housing H. As best shown in Fig. 5 each of the side rails Sti is of hollow rectangular construction with a pair of inwardly turned bottom flanges lrdening `a longitudinal bottom slot d2. Each of the suspension brackets 'i9 is in a form off aV metal bar that is twisted as shown in Fig. 5 to extend upward into the corresponding bottom slot of the corresponding side rail Si) `and the upper end of each suspension bracket carries a pair of rollers 33 that ride on the rail ilanges Si.

Preferably the yoke 64 is further provi-ded with a pair of spaced side rollers 87 on each side that roll along a flat metal bar mounted on the side wall of the housing below the corresponding side rail 3d. As shown in Fig. 6

each of the four side rollers 87 may be mounted on a corresponding arm b9 `which is pivoted by a bolt 90 on a corresponding fixed arm 91. Each of :the four xed arms 91 has an upwardly turned flange 92 through which is threaded a suitable adjustment screw 93 in abutment with the corresponding pivoted arm 89. It is apparent that thefour adjustment screws 93 may be sufficiently tightened against the four corresponding pivoted arms 89 to cause the four side rollers 87 to maintain guiding contact with the two side bars Sii.

Each of the two clamp means 7S comprises a hollow body 97` (Fig. 7) which serves as a socket to releasably hold an angular shoe 98 which is held in place by a dwell 133.

pair of cap screws 99; Each angular shoe 98 is pref'- erably provided with a liner 100 which may, for example, be a piece of belting and which serves the purpose of making non-slipping contact with the periphery of a pipe section P. It is contemplated that angular shoes 9d of different lengths will be available for use interchangeably in the two hollow bodies 97 to permit the two clamping means to grip pipe sections P of different diameters.

Each of the hollow bodies 97 has a cylindrical portion liti by means of which it is mounted on a corresponding vertical rocker shaft 102, the hollow body being held against rotation on the rocker shaft by a pair of screws 163. Each of the two rocker shafts 102 is mounted vertically in one of the legs 77 of the yoke dit with the lower end of the rocker shaft journalled in the lower flange 78 of the leg and with the upper end of the rocker shaft journalled in the transverse frame member *76 of the yoke. Keyed to the upper end of each or" the rocker shafts 192 is an operating arm 104 which is adapted for actuation by remote control in a suitable manner.

ln the construction shown in the drawings, one of the operating arms Mld is connected by a rod 105 to an air cylinder 1th? and the other operating arm is connected to a piston rod llt) that extends to a piston 111 inside the air cylinder. A pair of air lines 112 and 113 is connected to opposite ends of the air cylinder 109 for remote control of the air cylinder. For this purpose, as

'indicated in Fig. 9, the two air lines 112 and 113 may be connected respectively to the previously mentioned air lines o? and 69 that control the two side rams 60.

it is contemplated that the operation of the two clamp .means 75 will be correlated with the operation of the "two side rams 60 with the two clamp means opening slightly in advance of the forward retraction of the two yoke-controlling piston rods 63 and closing slightly in advance of the rearward extension movement of the two piston rods. Since the clamp-controlling air cylinder 169 is substantially smaller than the two yoke-controlling air cylinders 61 the desired correlation is inherent in the system. lf necessary, however, the air lines 112 and M3 may be relatively large for relatively rapid communication between the three-way valve 65 and the air cylinder 109, or the same effect may be achieved by restricting the rate of air flow between the three-way valve and the two air cylinders 61.

While the two threeway valves 55 and 65 may be separately manipulated by hand, preferably they are connected to a single central control on a control panel 125. in the particular arrangement illustrated by Figs. 9 and l0, for example, the two three-way valves 55, and 65 are controlled by a master control handle 116 which is carried by a cam disc 117. The cam disc 117 is rotatably mounted on a pivot 118 and is operatively connected with the two three-way valves. The operating member 57 of the three-way valve 55 is connected to a slide member 119 that is guided by four rollers 126 and, in like manner, the operating member 71 of the three-way valve 65 is connected to a second slide men: ber E21 guided by four rollers 122. The first slide member 119 carries a cam follower 123 that engages a cam slot 124i in the cam disc 117 and the second slide member 21 in like manner carries a cam follower 125 that engages a second cam slot 126 in the cam disc.

Cam slot 12d has a first outer dwell 13d, an intermediate dwell 131, an inner dwell 132 and a second outer At each of the two outer dwells 130 and 133 the follower 113.3 actuates the three-way valve 55 to extend the piston rod 52 of the central ram 49 and at the inner dwell 132 the cam follower 123 actuates the three-way valve to retract the piston rod forward. The intermediate dwell 131 corresponds to the neutral intermediate position of the three-way valve.

The other cam slot 126 has an outer dwell 134, an

intermediate dwell 135 and an inner dwell 136. When the cam follower 125 is in the outer dwell 134 the operating member 71 of the three-way valve 65 is actuated to extend the two yoke-actuating pistons 63 of the side rams 60 for rearward movement of the yoke 64 and when the cam follower is in the inner dwell 136 the three-way valve is actuated to retract the two yoke-actuating piston rods 63 to move the yoke 64 rearward. The intermediate dwell 135 corresponds to the intermediate neutral position of the three-way-valve. As heretofore explained, the air cylinder` 199 that controls the two clamp means '75 responds to operation of the three-way valve 65 by opening the two clamp means slightly in advance of the forward retraction of the two pistons 63 and by closing the two clamp means slightly in advance of the rearward extension of the two piston rods.

The manner in which oscillation of the cam disc 117 by the master control handle 116 correlates the operation of the various air cylinders 50, 61 and 169 may be understood by considering six control stations on the cam disc 117. These stations are represented respectively by six diametrical lines designated station 1, station 2, station 3, station 4, station and station 6. lWhen the two cam followers 123 and 125 are at station 1 the parts of the mechanism for applying longitudinal force to the pipeline are positioned as shown in Fig. 2. The two clamp means 75 are actuated by the air cylinder 109 to grip the latest added pipe section P of the pipeline and the two piston rods 63 actuated by the two side cylinders 61. exert continuous rearward thrust on the yoke 64 to cause the two clamp means 75 to maintain the pipeline under longitudinal compression. At this time the central ram 5t) is retracted to position the pusher plate 53 forward from the last added pipe section P of the pipeline. Thus at station 1 of the cam disc 117 space is provided for the positioning of a new pipe section in front of the pusher plate 53 as shown in Fig. 2.

When the operator swings the master control arm 116 to shift the two followers 123 and 125 through station 2 to station 3 the parts of the force-applying mechanism respond in the manner indicated by Fig. 3. The two clamp means 75 continue to grip the same pipe section as in Fig. 2 and the two air cylinders 61 continue to apply longitudinal force to the pipeline through the two piston rods 63. The piston rod 52 of the central ram, however, is now extended to force the pusher plate 53 against the new pipe section thereby causing the pipe section to slide along the V-shaped pipe guide 44 into interlocking engagement with the pipe section P that is gripped by the clamp means 75. Thus at station 3 the central rarn as well as the two side rams apply force to maintain the pipeline under longitudinal compression.

When the operator swings the master control handle 116 further clockwise to shift the two cam followers 123 and 12S through station 4 to station 5 the parts of the force-applying mechanism respond in the manner indicated in Fig. 4. The central ram continues to press the pusher plate 53 against the end of the last added pipe section P to maintain the pipeline under longitudinal compression but the two clamp means l5 open for disengagement from the pipeline and the two air cylinders 61 retract the two piston rods 63 to move the yoke 64 forward alongside the last added pipe section.

The operator now reverses the master control handle 116 counter-clockwise to rotate the cam disc back through station to station 3 with the result that the two clamp means-75 positioned as shown in Fig. 4 close to grip the last added pipe section P. Here again force is applied to the pipe line simultaneously by both the central ram and the two side rams, both forces in this instance being applied simultaneously to the last added pipe section. Thus the periods of force application by the central ram overlap the periods of force application by the two side rams.

The operator completes the operating cycle by moving the master control handle 116 further counter-clockwise to rotate the cam disc 117 back through station 2 to station 1 thereby causing the central ram to retract to provide room for a new pipe section as shown in Fig. l. Thus each cycle of operation for adding a new pipe section P to the pipe line without interrupting the application of longitudinal pressure to the pipeline is carried out simply by swinging the master control handle 116 first clockwise and then counter-clockwise to cause the cam disc 117 to rotate from station 1 to station 3, from station 3 to station 5, from station 5 back to station 3, and from station 3 back to station 1.

if the operator finds it necessary to retract both the central piston rod S2 and the two side piston rods 63 at the same time, for example at the start of laying a pipeline, he shifts the master control handle 116 to rotate the cam disc 117 to station 6, this station being shown in operative position in Fig. 10. At this station the follower 123 is in the second outer dwell 133 and the follower 125 is in the inner dwell 136. As a result, the two three-way valves 55 and 65 are actuated to retract the central piston rod 52 and to open the two clamp means 75 and retract the two side pistons 63.

Preferably suitable means is provided for normally preventing rotation of the cam disc 117 beyond station 5 to station 6. For example, a stop lever 137 having a handle 138 may be mounted on a pivot 139 and may be normally held by a suitable spring 140 against a stop lug 141 on the face of the cam disc. Normally the lever 137 is in abutment with the stop lug 141 to serve as a stop in cooperation with the cam follower 123 to block rotation of the cam disc beyond station 5. Whenever it is desired to rotate the cam disc 117 to station 6, the lever 137 may be swung out of the way.

As the housing H moves in tandem behind the ditch digger D it provides a moving pipe laying zone in the trench in the region of operation of the central ram 49 and the two side rams 60 and also provides an adjacent trailing gravel-packing zone into which gravel is dropped by the duct 40 from the gravel hopper 41. As the housing H moves along the newly dug trench the hopper 41 is continually replenished and new pipe sections P are lowered into the housing H on the inclined chute 42 as often as required. The operator inside the housing H simply reciprocates the master control handle 116 to oscillate the cam disc 117 between the two limit positions represented by stations 1 and 5 to carry out the previously described operating cycle repeatedly.

At the beginning of each operating cycle the operator transfers a new pipe section P from the delivery chute 42 to a position on the pipe guide in front of the installed pipeline as indicated in Fig. 2. When central ram 49 and the two side rams 60 are in operation, i. e. when they are both forcing the same or two adjacent pipe sections against the established pipeline at the same time, they gradually extend automatically at the rate of longitudinal forward movement of the housing H. As the gravel-packing compartment 36 shifts forward with movement of the housing H, gravel from the duct 40 gravitates around and under the installed pipe to extend the gravel bed 21 progressively. A bulldozer 142 operating behind the traveling housing forces the piled dirt 143 back into the trench to completely refill the trench above the level of the bed of gravel.

The two side walls 31 of the housing H keep the sides of the trench from caving in and the bottom wall 30 of the housing keeps the bottom of the newly dug trench from upheaval. As the trailing end of the bottom wall 30 of the housing uncovers the bottom of the trench, the gravel-packing compartment 36 moves over the exposed trench bottom to deposit gravel thereon and the deposited gravel transmits any upward upheaval forces against the underside of the pipeline. Thus the deposited gravel prevents upheaval by transmitting upheaval forces to the pipeline, the longitudinal compression of the pipeline being sufficient to resist any tendency for such upheaval forces to push the newly added pipe sections upward out of alignment with the installed pipe sections. As the housing H moves along to expose the bed of gravel 2li, the bulldozer 142 fills in the trench so that the weight of the filled-in earth on top of the bed of gravel becomes effective to prevent upheaval forces from forcing sections of the installed pipe upward. It is apparent, therefore, that the force applied by the forceapplying means in the pipe laying zone keeps the pipeline under longitudinal compression to resist upheaval forces until the trench is lled in toimpose such weight on the installed pipe as to permanently resist the upheaval forces. The soil in which the pipe laying operation is performed may be relatively wet and even semiuid without interfering with the described procedure and the functioning of the described apparatus.

it is to be noted that the method and apparatus of the invention is by' no means limited to the specific steps and structure shown and described. Obviously the invention may be practiced without the use of cam disc 117 since valves S5 and 65 or equivalents thereof may be operated manually and independently. Similarly, any convenient means other than chute d2' may be employed to introduce pipe into the housing H. Still further, pipe guard ld may take any convenient shape and need not necessarily be used at all.

My description in specific detail of the presently preferred practice of the invention set forth herein by way of example to illustrate the principles involved, will suggest to those skilled in the art, various other changes, substitutions and other departures from my disclosure that properly lie within the spirit and scope of the appended claims.

Having described my invention, I claim:

1. A method of laying pipe underground for draining wet soil, including the steps of: Digging a trench; positioning a first pipe section against the forward end of an established pipe; applying a force to the forward portion of said pipe section to press the pipe section against the established pipeline; positioning a second pipe section against the first-mentioned pipe section; applying force to the forward portion of the second pipe to press the second pipe section longitudinally against the first pipe section; releasing the first applied force while maintaining the second applied force; repeating these steps of positioning successive pipe sections and applying force to the successive sections of pipe with the successive applications of force overlapping thereby to maintain the leading end of the pipe line under uninterrupted longitudinal pressure; and pouring material into the trench to surround and immobilize each successive pipe section while it is under longitudinal pressure.

2. A method of laying pipe underground for draining wet soil, including the steps of: digging a trench; establishing an initial length of buried pipeline in said trench; positioning a rst pipe section against the forward end of the established pipeline; applying a force to said first pipe section to press it against the established pipeline; positioning a second pipe section against said first pipe section; applying a force to said second pipe section to press it longitudinally against said first pipe section; releasing the first applied force while maintaining the second applied force; repeating the steps of positioning successive pipe sections and applying force to the successive sections of pipe with the successive applications of force overlapping thereby to maintain the leading end of the pipe-line under uninterrupted longitudinal pressure; and pouring material into the trench to surround and immobilize each successive pipe section while it is 'under longitudinal pressure,

3. A method of laying pipe underground, including the steps of: digging a trench; establishing an initialv length of pipe in said trench; positioning a first pipe section against the forward end of the established pipe; applying a first force to' said first pipe section to press it against the established pipe; applying a second force to the same first pipe section also to press it against the established pipe while maintaining the first applied force to said first pipe section; releasing the first force applied to said first pipe section while maintaining the second force applied to said rst pipe section; positoning a second pipe section against said first pipe section; applying a first force to said second pipe section to press it against said ifirst pipe section while maintaining said second applied force on said first pipe section; releasing said second applied force on said first pipe section while maintaining said first applied force on said second pipe section; applying a second force to said second pipe section also to press it against said first pipe section while maintaining said first applied force on said second pipe section; releasing said first applied force on said second pipe section while maintaining said second applied force on said second pipe section; repeating these steps of positioning successive pipe sections and applying force to successive sections of pipe with the successive applications of force overlapping both on the same pipe section and onto adjacent pipe sections, thereby to maintain the leading end of the pipeline under uninterrupted longitudinal pressure; and pouring material into the trench to surround and immobilized said pipe section.

4. A method of laying pipe underground, including the steps of: digging a trench; establishing an initial length of pipe in said trench; positioning a first pipe section against the forward end of the established pipe; applying a first force to said first pipe section to press it against the established pipe; applying a second force each side of the same first pipe section also in a direction to press it against the established pipe while maintaining the first applied force to said first pipe section, said second applied forces to said first pipe section having components normal to said first pipe section on each side thereof to seize it securely while pressing it against the established pipe; releasing the first force applied to said first pipe section while maintaining the second forces applied to said first pipe section; positioning a second pipe section against said first pipe section; applying a first force to said second pi e section to press it against said first pipe section While maintaining said second applied forces on said first pipe section; releasing said second applied forces on said rst pipe section while maintaining said first applied force on said second pipe section; applying a second force to each side of said second pipe section also in a direction to press it against said first pipe section while maintaining said first applied force on said second pipe section, said second applied for-ces to said second pipe section having components normal to said second pipe section on each side thereof to seize it securely while pressing it against said first pipe section; releasing said first applied force on said second pipe section while maintaining said second applied forces on said second pipe section; repeating these steps of postioning successive pipe sections and applying force to successive sections of pipe with the successive applications of force overlapping both on the same pipe section and onto adjacent pipe sections, thereby to maintain the leading end of the pipeline under uninterrupted longitudinal pressure; and pouring material into the trench to surround and immobilize said pipe sections.

5. A method of laying pipe underground, including the steps of: digging a trench; establishing an initial length of pipe in said trench; positioning a first pipe section against the forward end of the established pipe; applying a first force to each side of said first pipe section in a direction to press it against the established pipe, said first forces having components normal to the longitudinal axis of said pipe section on each side to seize it securely while it is pressed against the established pipe by components in the direction of the longitudinal axis of said pipe section; positioning a second pipe section against the first-mentioned pipe section; applying a force to said second pipe section to press it longitudinally against the first pipe section; releasing the first applied forces while maintaining the second applied forces; repeating the steps of positioning successive pipe sections and applying force to the successive sections of pipe with the successive applications of force overlapping, thereby to maintain the leading edge of the pipeline under uninterrupted longitudinal pressure; and pouring material into the trench to surround and immobilize said pipe sections.

6. A method of laying pipe underground for draining wet soil, including the steps of: digging a trench; positioning a first pipe section against the forward end of an established pipe; applying a force to the forward portion of said pipe section to press the pipe section against the established pipeline; positioning a second pipe section against the irst-mentioned pipe section; gripping the forward portion of the second pipe section and applying a longitudinal force to said second pipe section to press it against the iirst pipe section while simultaneously References Cited in the le of this patent UNITED STATES PATENTS 1,174,271 Perry Mar. 7, 1916 1,463,561 Sommer July 31, 1923 1,600,701 Sommer Sept, 2l, 1926 1,792,855 McRae Feb. 17, 1931 2,106,469 Seil Jan. 25, 1938 2,738,745 Harpold Mar. 20, 1956 

